Field of the Invention
This invention relates to an ebullient cooling device.
Background Art
An ebullient cooling device that performs cooling in an internal combustion engine by utilizing boiling/evaporative heat of a coolant that is caused to flow in a coolant passage (for example, a water jacket) that is formed inside the internal combustion engine has already been disclosed in, for example, Japanese Patent Laid-Open No. 2008-248703 or Japanese Patent Laid-Open No. 61-275522. In the aforementioned ebullient cooling devices, the coolant passage constitutes one part of a closed circuit that circulates a coolant, and a condenser and a water pump are provided partway along the closed circuit. A gas-phase coolant that is discharged from the coolant passage is cooled by the condenser and returns to a liquid-phase coolant which is then fed to the coolant passage by the water pump.
Further, Japanese Patent No. 5003725 discloses an ebullient cooling device that includes, between a coolant passage and a condenser, a gas-liquid separator that separates coolant that is discharged from the coolant passage into gas-phase coolant and liquid-phase coolant. In this ebullient cooling device, the coolant passage, the gas-liquid separator and a first water pump constitute one part of a closed circuit that circulates a coolant. The liquid-phase coolant inside the gas-liquid separator is fed to the coolant passage by the first water pump. Furthermore, in this ebullient cooling device, the condenser constitutes one part of another closed circuit that circulates coolant between the condenser and the gas-liquid separator. The gas-phase coolant that is separated by the gas-liquid separator is cooled by the condenser and returns to a liquid-phase coolant, and is then fed to the gas-liquid separator by a second water pump.
In the ebullient cooling device described in Japanese Patent No. 5003725, if the pressure inside the gas-liquid separator is rapidly decreased, in some cases intense boiling will occur with respect to the liquid-phase coolant inside the gas-liquid separator. In this case, because the gas-liquid separator is connected to the first water pump, if intense boiling occurs in the liquid-phase coolant inside the gas-liquid separator, there is a possibility that intense boiling will also occur in the liquid-phase coolant that is immediately upstream of the first water pump. If intense boiling occurs in the liquid-phase coolant that is immediately upstream of the first water pump, the first water pump will run idle and there will be a decrease in the flow rate of the coolant that should be fed into the coolant passage from the first water pump, and hence the problem of insufficient cooling of the engine will arise.